I have an orchestration that receives an XML with some email properties(like: to, from, cc, subject, etc..).
Then I want to send the emailmessage with a dynamic port (and I assigned some of the values according the input xml). After the email has been sent, I want to do some further processing but that processing may only execute when the mail has been delivered succesfully on the SMTP server.
In the functional design they want to have a retry per hour and maximum of one day, after that periode a message must be in the EventLog when it cannot be delivered successfully.
Therefore I set the dynamic port with the context properties BTS.RetryCount to 23 and BTS.RetryInterval to 60.
I have set the dynamic SMTP port delivery notification to "Transmitted" and I have a catch exception block to catch the DeliveryFailureException.
Is this enough ?
It is a litte bit confusing for me reading several blogs if I should mark the scope Synchronized...
Patrick,
You're right, the documentation on this aspect of BizTalk delivery notification is scarce and confusing. After extensive testing, I have not been able to identify a difference wether the Scope is set to Synchronized = true; or not.
The official documentation for the Synchronized setting only applies to shared variables when used in both branches of a Parallel execution.
As for the Delivery Notification itself, I'm currently facing a problem in production where the FILE adapter produces its ACK event before the entire contents of the file is written to the output folder - it renders this part of the solutiong useless!
Related
I use AMQ 6 (ActiveMQ) on OpenShift, and I use a queue with re-delivery with exponentialBackoff (set in connection query params).
When I have one consumer and two messages and the first message gets processed by my single consumer and does NOT get an ACK...
Will the broker deliver the 2nd message to the single consumer?
Or will the broker wait for the re-delivery to preserve message order.
This documentation states:
...Typically a consumer handles redelivery so that it can maintain message order while a message appears as inflight on the broker. ...
I don't want to have my consumer wait for re-delivery. It should consume other messages. Can I do this without multiple consumers? If so, how?
Note: In my connection query params I don't have the ActiveMQ exclusive consumer set.
I have read the Connection Configuration URI docs, but jms.nonBlockingRedelivery isn't mentioned there.
Can the resource adapter use it by query param?
If you set jms.nonBlockingRedelivery=true on your client's connection URL then messages will be delivered to your consumer while others are in the process of redelivery. This is false by default.
Here is what I gathered from the RFC 5321:
4.1.1.5. RESET (RSET)
This command specifies that the current mail transaction will be aborted. Any stored sender, recipients, and mail data MUST be discarded, and all buffers and state tables cleared. The receiver MUST send a "250 OK" reply to a RSET command with no arguments. A reset command may be issued by the client at any time. It is effectively equivalent to a NOOP (i.e., it has no effect) if issued immediately after EHLO, before EHLO is issued in the session, after an end of data indicator has been sent and acknowledged, or immediately before a QUIT.
The emphases are mine. This says that if we receive the RSET after the end of data indicator ".", but before we sent the acknowledgement, then we must discard the content of the message, which is currently being delivered. This does not seem practical. Moreover, the server can easily acts as if it received the RSET after he sent the acknowledgement - the client would not be able to know. Trying to know what is usually done, I found this discussion https://www.ietf.org/mail-archive/web/ietf-smtp/current/msg00946.html where they say:
Under a RFC5321 compliant "No Quit/Mail" cancellation implementation, after
completing the DATA state, the server is waiting for a pending RSET, MAIL
or QUIT command:
QUIT - complete transaction, if any
MAIL - complete transaction, if any
perform a "reset"
RSET - cancel any pending DATA transaction delivery,
perform a "reset"
drop - cancel any pending DATA transaction delivery
We added this support in 2008 as a local policy option (EnableNoQuitCancel)
which will alter your SMTP state flow, your optimization and now you MUST
follow RSET vs QUIT/MAIL correctly. RSET (after DATA) aborts the
transaction, QUIT/MAIL (after DATA) does not. RSET is not an NOOP at this
point.
The specification says that discarding is a MUST. However, the above extract suggests that in practice it is interpreted as a MAY. I could look at the code of known implementations of SMTP/LMTP, such as Dovecot, but perhaps someone already reviewed that and this would save me time.
The text says "end of data indicator has been sent and acknowledged" which suggests that the client has received the server's response to the DATA command. Since the base protocol doesn't support command pipelining, I don't think sending anything after DATA but before the server's response (after the dot which terminates the DATA but before you receive a reply from the server) is well-defined behavior.
Personally, I can't think of any more reasonable server behavior than "pretend it didn't happen."
The answer is here : https://www.rfc-editor.org/rfc/rfc1047 . They basically says that you can acknowledge before you start the processing and it is actually recommended to do so. This does not violate RFC 5321. Of course, more information on this issue would be useful, but I am happy with rfc1047.
Thinking of 'production' usage of Orion Context Broker, I wonder what kind of guarantees are provided by the Orion Context Broker in terms of delivery of messages -- both from producer and consumer perspective? In particular, keeping in mind various possible failure scenarios (CB failure/restart, network transient failure, consumer failure/restart, etc), as well as possibility of resource congestion in the CB. Few examples:
1) if a context update operation succeeds, is it guaranteed that consequent queries will return the latest data (e.g., even if CB failed right after acknowledging the update request, and then restarted)?
2) if a consumer subscribed for certain context information, is it guaranteed that it will receive all the relevant updates -- exactly once, at least once, or even at all? (e.g., in case of transient network failure between CB and the consumer)
3) if a consumer updated its subscription, is it guaranteed that the consequent updates will accurately reflect it? (e.g., if CB failed right after acknowledging the subscription request, and then restarted)
4) if a consumer is subscribed for context changes ('onchange', no throttling), and there are multiple consequent updates from the producer affecting the same attribute, is it guaranteed that each of the changes will be sent (or some might be skipped -- e.g., due to too many notifications that CB needs to send during a certain period of time), in any particular order?
etc...
Thanks!
Answering bullet by bullet:
In general, if the client receives a 2xx response (inside of the response payload in the case of NGSIv1, HTTP response code in the case of NGSIv2) it can assume that the update has been persisted in context database, so subsequent queries will return that data (except in the case of running CB with -writeConcern 0 if the DB fails before the update can be persisted from DB memory to disk).
In order to keep things simpler, CB uses a "fire and forget" notification policy. However, CB can be combined with HTTP relaying software (e.g. Rush, event buses, etc.) in order to implement retries, etc.
Similar to case 1, if the client receives a 2xx response (inside of the response payload in the case of NGSIv1, HTTP response code in the case of NGSIv2) it can assume that the update has been persisted in context database (except in the case of running CB with -writeConcern 0 if the DB fails before the update can be persisted from DB memory to disk), so notifications of such data (due to either existing subscriptions or new ones) will use the new value.
All notifications will be sent as long as thread saturation (in the case of -notificationMode transient) or queue saturation (-notification threadpool:q:n) don't occur. You can find more information about notification modes in Orion documentation.
import socket
def functions():
print ("hello")
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_address = ('192.168.137.1', 20000)
sock.bind(server_address)
sock.listen(1)
conn, addr = sock.accept()
print ('Connected by', addr)
sock.listen(1)
conn.sendall(b"Welcome to the server")
My question is how to send a function to the client,
I know that conn.sendall(b"Welcome to the server") will data to the client.
Which can be decoded.
I would like to know how to send a function to a client like
conn.sendall(function()) - this does not work
Also I would like to know the function that would allow the client to receive the function I am sending
I have looked on the python website for a function that could do this but I have not found one.
The functionality requested by you is principally impossible unless explicitly coded on client side. If this were possible, one could write a virus which easily spreads into any remote machine. Instead, this is client right responsibility to decode incoming data in any manner.
Considering a case client really wants to receive a code to execute, the issue is that code shall be represented in a form which, at the same time,
is detached from server context and its specifics, and can be serialized and executed at any place
allows secure execution in a kind of sandbox, because a very rare client will allow arbitrary server code to do anything at the client side.
The latter is extremely complex topic; you can read any WWW browser security history - most of closed vulnerabilities are of issues in such sandboxing.
(There are environments when such execution is allowed and desired; e.g. Erlang cookie-based peering cluster. But, in such cluster, side B is also allowed to execute anything at side A.)
You should start with searching an execution environment (high-level virtual machine) which conforms to your needs in functionality and security. For Python, you'd look at multiprocessing module: its implementation of worker pools doesn't pass the code itself, but simplifies passing data for execution requests. Also, passing of arbitrary Python data without functions is covered with marshal and pickle modules.
I am using NServiceBus for the first time and have a small, simple application where a user submits a form, the form fields are then sent to the queue, and the handler collects this data and writes it to the database using linq-to-sql.
Any changes within Component Services is a complete no-no as far as the DBA is concerned, so I'm now looking for an alternative to DTC (which is not enabled on the DB server), but using AsA_Server so that messages do not get purged.
I have tried removing AsA_Server after IConfigureThisEndpoint and specifying the configuration myself, but this doesn't seem to work (the console appears, page loads but nothing happens, it doesn't even stop at breakpoints.) AsA_Client does work, but as I understand it the messages will be purged at startup which I need to avoid.
Any suggestions?
Thanks,
OMK
EDIT: This has now been resolved by using wrapping the call to the database in a suppress transaction scope, which allows the database work to be done with no ambient transaction to enlist in:
using (TransactionScope sc = new TransactionScope(TransactionScopeOption.Suppress))
{
// code here
sc.Complete();
}
When you use AsA_Server, you are specifying you want durable queues and you will need to configure transactional queues.
With a transactional send/receive MSMQ requires you to send, transmit, receive, and process as part of one transaction. However, actually all these stages take place in their own transactions.
For example, the send transaction is complete when the sender sends a message onto their local MSMQ subsystem (even if the queue address is remote, the sender still sends to a local queue which acts as a kind of proxy to the remote queue).
The transmit transaction is complete when the MSMQ subsystem on the senders machine successfully transmits the message to the MSMQ subsystem on the receivers machine.
Even though this may all happen on one machine, I am guessing that your Handle() method is writing to a database on a different machine.
The problem here is that for the receive operation to complete satisfactorily from a transaction perspective, your call to the database must be successful. Only then will the message be de-queued from your input queue. This prevents any chance that the message is lost during processing failure.
However, in order to enforce that across the network you need to involve DTC to coordinate the distributed transaction to the database.
Bottom line, if you want durable queues in a distributed environment then you will need to use MSDTC.
Hope this helps.
There is an alternative. In your connection string you can add the option to not enlist in a distributed transaction and this will have your DB connection ignored in the DTC.
Of course, if this is set in the config then all database transactions for the application are ignored by the DTC rather than just a specific one.
Example:
<add key="DatabaseConnectionString" value="Data Source=SERVERNAME;Initial Catalog=DBNAME;Integrated Security=True;Enlist=False"/>
With NServiceBus 4.0 you can now do the following, which finally worked for me:
Configure.Transactions.Advanced(t =>
{
t.DisableDistributedTransactions();
t.DoNotWrapHandlersExecutionInATransactionScope();
});
When you use the As (AsA_Client, AsA_Server) interfaces, the configuration is applied after Init() so all the settings that you make there regarding MsmqTransport and UnicastBus are overriden.
It's possible to override those settings using IWantTheConfiguration in a IHandleProfile implementation. You get the Configuration after the default roles are applied but before the bus is started.
This way you can change the default profile settings and tailor them to your needs: deactivate transactions, enable impersonation...
Example:
public class DeactivateTransactions : IHandleProfile<Lite>, IWantTheEndpointConfig
{
private IConfigureThisEndpoint configure;
public IConfigureThisEndpoint Config
{
get { return configure; }
set
{
this.configure = value;
Configure.Instance.MsmqTransport()
.PurgeOnStartup(false)
.IsTransactional(false); // Or other changes
}
}
public void ProfileActivated()
{
}
}